The present invention relates to a gas cleaning apparatus of the bag filter type that removes dust and other particulate matter from a gas stream by passing the gas through a porous fabric filter bag. More specifically, the present invention relates to a bag tensioning apparatus which is readily releasable to allow removal and replacement of the filter bags.
A typical baghouse filter is constructively a plurality of filter bags suspended in an enclosure termed a baghouse. Each filter bag is a cylindrically elongated porous fabric member having an open end which is attached to a tube sheet and a closed end which is suspended from a support beam. The filter bags and the tube sheet divide the baghouse into two chambers, one chamber comprising the space external to the bags and the other chamber comprising the space internal to the bags.
In operation, a gas laden with entrained solid particles is drawn through the baghouse. Entering through one chamber as dirty gas, the gas passes through the fabric filters to leave through the other chamber as a clean gas. As the gas flows through the fabric, the entrained solid particles being too large to pass through the pores of the fabric, collect on the surface of the fabric and are, thereby, filtered from the gas.
When suspended from the support beam, it is desirable that a predetermined amount of tension be placed on the bags so that the fabric of the bag is kept in a uniformly taut condition to ensure optimum collection efficiency. However, when the bags are subjected to service for even a short period of time, the filter cloth from which they are constructed collects a quantity of dust that sharply increases the pressure drop across the bags and increases their resistance to gas flow through the fabric. Inasmuch as these dust deposits must be periodically removed from the bags by shaking them or subjecting them to reverse air flow, the bags stretch, loosen, and wear until they are no longer taut; and their collecting efficiency is severely impaired. Thus, the bags must be replaced with new bags when they become excessively worn or when the fabric has deteriorated from repeated cleaning.
To provide for proper bag tensioning, the filter bags are typically suspended from the support beam by means of a spring biased threaded hanger rod which extends axially through the support beam and is pivotally connected to the closed end of the filter bag. A nut is threaded onto the hanger rod and tightened so as to compress the spring between the nut and the support beam until the desired tension on the bag is achieved. Although this apparatus is capable of providing proper and uniform pretensioning of the bags, removal of the bags is a laborious operation. When it is desired to remove the bags, the nut must be completely unthreaded so as to remove all tension on the bags. The bags may then be manually removed and new bags connected to the hanger rod. The nut must be then threaded back on to the rod and tighten down to again properly pretension the bags.
The present invention, therefore, has as its general objective to provide a bag tensioning apparatus of the spring biased threaded hanger rod type which permits the bags to be quickly removed and replaced without disassembly of the bag tensioning apparatus.